This invention relates to a low-temperature dry etching method. More particularly, it relates to a low-temperature dry etching method which is suited for high-precision dry etching and in which etching is carried out by controlling the surface temperature of the article to be etched.
According to the conventional dry etching methods, in order to accomplish vertical etching with minimized side etch, it has been practiced to form a protective film on the side wall of the etched pattern to prevent side etch, as for instance described in Japanese Patent Application Laid-Open (Kokai) No. 126835/85, thereby to improve the etching precision. Also, as means for adsorbing etching gas on the article surface for strengthening so-called ion-assisted etching in which etching is carried out by having neutral particles adsorbed on the wafer surface and applying ions thereto, it has been practiced to regulate the article surface temperature so that the vapor pressure of the reaction product in the course of etching would become 1/10 of the vapor pressure at room temperature and to carry out etching at a temperature below said article surface temperature to thereby increase the etching speed, as for instance described in Japanese Patent Application Laid-Open (Kokai) No. 158627/85.
Among said prior art techniques, the technique for vertical etching intended to prevent side etch by forming a protective film on the side wall has many problems due to the utilization of deposition of the reaction product or the polymer formed by etching gas. For example, according to this technique, the etching reaction rate is lowered in principle, necessitating much time for the etching- Also, since the deposition film is formed not only on the side face of the wafer but also everywhere on the inner wall of the apparatus, such film would become a source of filthiness as it comes off to contaminate the wafer. Further, the film deposited on the pattern side wall must be removed after the formation of pattern, but such film removal is actually quite troublesome. Thus, this technique could hardly be applied to practical use in the production of semiconductor devices because of too low throughput and high level of defectiveness due to alien matter deposited on the wafer surface.
The idea of cooling the wafer for promoting the effect of ion assistance is merely envisaged to have the reaction gas adsorbed on the article surface and no regard is given to the possible change of vapor pressure of the reaction product and etching gas according to the temperature, so that this technique also has the problems such as lowered etching speed due to low temperature.